The present invention relates to novel acetanilide derivatives of the following formula (I): ##STR3## (wherein R.sup.1 is a lower alkyl group; R.sup.2 is a fluorine-substituted lower alkyl group; A is ##STR4## B is an optionally substituted pyrazolyl group, an optionally substituted alkoxy group or a hydrogen atom), as well as a herbicide containing one or more of these acetanilide derivatives as the active ingredient.
Haloacetanilides having herbicidal or growth controlling actions are known. For instance, U.S. Pat. No. 3,547,620 discloses 2-chloro-2',6'-diethyl-N-methoxymethyl acetanilide (hereunder abbreviated as compound A), and Unexamined Published Japanese Patent Application No. 53651/78 discloses 2-chloro-2',6'-dimethyl-N-pyrazolylmethyl acetanilide (hereunder abbreviated as compound B).
Chloroacetanilide compounds of the type shown above generally exhibit herbicidal effects on monocotyledonous plants when applied in soil treatment. For example, compound B as applied to the treatment of soil in upland farm exhibits good herbicidal activities but is very poor in selectivity for crop species. On the other hand, compound A is currently used in actual crop fields on account of its high selectivity for corn (Zea mays), soybean (Glycine max) and cotton (Gossypium hirsutum). However, the herbicidal activity of compound A is relatively low as compared with compound B and needs further enhancement.